This is from another sit I fitted it and its plug and play no cutting anything takes 10 minutes
I purchased a VW iPod adapter for my Golf GTi 5. Its this one.
My car was originally fitted with a CD Changer in the armrest. I removed this and replaced it with Part number:1KO 857 925 A 1QB which comes up as a Shelf on the parts system. This is for a Right Hand Drive Golf Mk V.
Remove the changer and then disconnect the lead attached to the bottom of it. The iPod adapter then has the exact same connector on it. Attach that to the connector on the base of the unit.
The Radio/Navi will then see the iPod adapter as a CD Changer and playlists appear on the radio as CD's The iPod is charged in the unit. There are some electronics in the base of the unit.
My dealer in the UK was told that this was not a UK Part and as such was not supposed to order it. However they did and it arrived in a few days. There is another part marked as adapter but I ordered it, as yet it has not arrived. I think it might be for the iPod mini - my Gen 5 iPod is a bit loose in the holder but other than that it works fine.
Edit:
The Adaptor arrived today - some 10 weeks after ordering. It is infact a bank of adapters to suit different iPods, there is one for the Gen 5 iPod, the Nano, the Mini and the other types of iPods as well therefore if you have problems with your iPod fitting then you will need the adapter pack - See below for the part number
There is also a VW USB one which takes USB memory sticks that contain WMA MP3 and OGG Vorbis Files which also can be used. I dont have this one but I assume that it works the same.
Hope this helps